Apparatus for decontaminating hydraulic systems



Feb. 13, 1968 l. R. KRAMER APPARATUS FOR DECONTAMINATING HYDRAULICSYSTEMS Filed April 30, 1962 ED E Qsqk QSE Sui INVENTOR. IRVIN R. KRAMERATTORNEY United States Patent 3,368,962 APPARATUS FOR DECONTAMINATINGHYDRAULIC SYSTEMS Irvin R. Kramer, Baltimore, Md., assigmor to Martin-Marietta Corporation, Baltimore, Md., a corporation of Maryland FiledApr. 30, 1962, Ser. No. 191,122 9 Claims. (Cl. 204299) My inventionrelates to hydraulic systems and, more particularly, to a method and ameans whereby impurities in a high dielectric constant fluid areprevented from accumulating at critical points in a hydraulic system andare removed therefrom.

The terms critical points, critical areas and critical parts as I haveused them herein shall be understood to refer to particular sections ofa hydraulic system wherein an accumulation of foreign particles may beexpected to adversely affect system operation. The hydraulic systemsreferred to herein shall be understood to be systems utilizing a highdielectric constant fluid.

Foreign particles present in hydraulic fluids often cause unsatisfactorysystem operation and may result in complete system failure. It isimportant that hydraulic fluids be maintained relatively free of suchimpurities and further that any impurities, which are initially presentin the fluid or which develop in the course of operating such systems,be prevented from accumulating at the critical areas of the system. Manytechniques have been developed and are presently being utilized todecontaminate hydraulic fluids. All of these methods employ a means forcollecting the foreign particles at a designated point in the system.However, very little attention has been devoted to the problem ofautomatically removing impurities from critical areas where they havecollected and/ or to preventing the accumulation of such particles inthese areas in the first instance. Consequently, even though theseproblems have long been recognized, the critical applications being madeof hydraulic systems in todays space age are continually emphasizing thelimitations of systems heretofore devised.

Contaminating agents in hydraulic fluids generally comprise fineparticles suspended in the fluid. I have determined that these particlespossess an electrical charge, some being positively charged While othersare negatively charged. My invention, hereinafter described inconsiderable detail, takes advantage of this phenomenon to furnish asimple and extremely effective method for decontarninating dielectrichydraulic fluids. One of the features of my invention is the collectingof foreign particles from the fluid and it will be seen that otherfeatures of my invention, While primarily performing other and novelfunctions, in effect cooperate to accelerate this process.

It is therefore the primary object of the present invention to provide amethod for preventing foreign particles in a hydraulic fluid system fromaccumulating at critical points of the system. An additional object isto provide a method whereby foreign particles present in a hydraulicfluid system may be effectively removed therefrom. Another object is toprovide a simple and efficient means whereby foreign particles initiallypresent in the hydraulic fluid or which develop in the course of systemoperation may be prevented from accumulating at critical points of thesystem and continually and effectively removed from the system. Theseand other objects and advantages of my invention will become apparent asthe following description is read in connection with the accompanyingdrawings in which:

FIGURE 1 is a diagrammatic view of a typical section of a hydraulicsystem incorporating the principles of my invention;

3,368,962 Patented Feb. 13, 1968 FIGURE 2 is a diagrammatic view showingthe principles of my invention being utilized to prevent theaccumulation of foreign particles on the critical areas of an angleneedle valve; and

FIGURE 3 is another diagrammatic view showing the principles of myinvention being utilized to assure the reliable operation of a fixedorifice.

My invention basically contemplates placing an alternating electricalcharge on the critical areas of a hydraulic system to repel electricallycharged foreign particles away from such areas and collecting theseparticles on positively and negatively charged electrodes immersed inthe hydraulic fluid at a selected point.

Referring first to FIGURE 1, a section of a typical hydraulic system isshown in which a check valve 4 has been connected to piping 5 by acoupling sleeve 6. In the type of check valve illustrated, a poppet 7 isseated against a valve body 8 by the force exerted on it by a spring 9.When the fluid pressure on a face 10 of the poppet 7 is sufficient toovercome the force of the spring 9, the valve is opened by the poppetsbeing displaced in the direction of the fluid flow. The fluid then flowsthrough the ports 11 provided in the poppet 7, into chamber 12 and onthrough the hydraulic system. In the closed position, I seat the poppet7 against a cylindrical member 13- which is disposed in a recess 14provided in the valve body 8. Interposed between the cylindrical member13 and the valve body 8 is a sleeve 15 of rubber or any other suitabledielectric material. A bearing surface 16 of the cylindrical member 13is tapered to the same angle as the conical annular edge 17 of thepoppet 7 in order that there will be no flow of fluid through the valvewhen the poppet is seated against the cylindrical member 13. A source ofalternating electrical energy 18 has one of its terminals connected tothe cylindrical member 13 by a line 19, which passes through an aperture20 suitably provided in the valve body 8. The other terminal of thesource of alternating electrical energy 18 is connected to ground at 21.

A tank 22 is connected to the check valve 4 by the coupling sleeve 23and to the piping 5 by the coupling sleeve 24. The tank 22 is open atthe top, being provided at this point with an outwardly extendingannular projection 25. It should be noted that this tank 22 may be infact the systems fluid storage tank. A cover 26 seats on the outwardlyextending annular projection 25 of the tank 22, a gasket 27 beinginterposed therebetween so as to provide an effective seal for thehydraulic fluid contained in the tank. A plurality of bolts 28, whichpass through holes suitably provided in the cover 26, the gasket 27 andthe annular projection 25, fasten the cover 26 to the tank 22maintaining the necessary pressure on the gasket 27. The cover 26 isprovided with two cylindrical bores 29 and 30 which pass therethrough.Extended into the tank 22 through the cylindrical bores 29 and 30 aretwo electrodes 31 and 32. The electrodes 31 and 32 are made of anysuitable conductive'material, such as copper, and are provided withextensions 33 and 34. Interposed between the electrodes 31 and 32 andthe cover 26 are sleeves 35 and 36 which also are provided withextensions 37 and 38, said extensions 37 and 38 being interposed betweenthe electrode extensions 33 and 34 and the tank cover 26. The sleeves 35and 36 are of rubber or any other suitable material which serves both asan electrical insulator and as a hydraulic seal. A plurality of screws39 pass through holes provided in each of-the electrode extensions 33and 34 to secure the electrodes 31 and 32 to the tank cover 26. Thescrews 39 are suitably insulated (not illustrated) from the electrodes31 and 32 in order that there will be no electrical connection betweenthe electrodes and the tank cover 26. A source of direct electricalenergy 40 is 3 connected to the electrodes 31 and 32 at points 41 and42, respectively.

The most critical area of the check valve 4 is the hearing surface 16against which the poppet 7 seats to prevent the flow of fluid throughthe valve. Should foreign particles accumulate on the bearing surface16, the poppet 7 will not scat properly and leakage will occur. Inoperation, the cylindrical member 13 of the check valve 4 is connectedto the source of alternating electrical energy 18 and the electrodes 31and 32 are connected to the source of direct electrical energy 40 asillustrated in FIGURE 1. It will thus be seen that the cylindricalmember 13, and most important the bearing surface 16 thereof, will bealternately charged with a positive and negative potential. In addition,the electrode 31 will be charged with a positive potential whileelectrode 32 will be charged with a negative potential. The hydraulicfluid flows through the system carrying positively and negativelycharged foreign particles through the check valve 4 and into the tank22. When the cylindrical member 13 is positively charged, positivelycharged foreign particles present in the hydraulic fluid in the vicinitythereof will be repelled away from the bearing surface 16 toward thecenter of the hydraulic stream and carried thereby away from this area.When the cylindrical member 13 becomes negatively charged, negativelycharged foreign particles present in the hydraulic system in thevicinity thereof will be repelled away from the bearing surface 16toward the center of the hydraulic stream and carried thereby away fromthis area. This action prevents foreign particles carried by thehydraulic fluid from accumulating on the bearing surface 16, thecritical area of the check valve 4.

As the foreign particles suspended in the hydraulic fluid are carriedthereby into the tank 22, those which are positively charged areattracted by and collected on the surface of the electrode 32.Simultaneously, those which are negatively charged are attracted by andcollected on the surface of the electrode 31. At convenient intervals inthe systems operation when the hydraulic system can be or is shut down,the tank cover 26 with the electrodes 31 and 32 mounted thereon isremoved from the tank 22 after first unfastening the bolts 28. Theforeign particles are removed from the electrodes 31 and 32 and thecover 26 replaced on the tank 22.

In FIGURE 2, a typical section of a hydraulic system has beenillustrated consisting of piping 43 and an angle needle valve 44. Thepiping 43 is electrically insulated from the needle valve 44 by use ofplastic coupling sleeves 45 and rubber gaskets 46 or by any othersuitable means. A handle 47 is formed of any non-conducting materialsuch as plastic. The needle valve 44 is connected to one of theterminals of a source of alternating electrical energy 48 by a line 49.The other terminal of the source of alternating electrical energy 48 isconnected to ground at 50. A needle 51 seats against a similarly taperedbearing surface 52 of the valve body 53 and, in order to insure properoperation of the valve, foreign particles should be prevented fromaccumulating in this area. It will be seen that when the needle valve 44is connected to the source of alternating electrical energy 48 asillustrated in FIGURE 2, the needle 51 and the bearing surface 52 willbe alternately charged with a positive and a negative potential. Whenpositively charged, positively charged foreign particles present in thehydraulic fluid in the vicinity of these parts of the needle valve 44will be repelled from the surfaces of these parts toward the center ofthe hydraulic stream and carried thereby away from this critical area ofthe valve. Similarly, negatively charged foreign particles present inthe hydraulic fluid in the vicinity of these parts of the needle valve44 will be repelled from the surface of these parts toward the center ofthe hydraulic stream and carried thereby away from this critical area ofthe valve, when these parts become negatively charged. This alternatingcharge prevents foreign particles from accumulating on either thebearing surface 52 or the needle 51 and permits the proper seating ofthe needle when it is intended that the valve should cut-off the flow offluid through the system.

My invention is particularly useful in assuring the reliable operationof fixed orifices such as those which are employed in most servo valves.Referring to FIGURE 3, a typical fixed orifice 54 is shown positioned ina tubular member 55. However, in my invention, I form the orifice 54 ofan electrical conducting material and insulate the orifice from thetubular member 55 by a sleeve 56 of rubber or any other suitabledielectric material. The orifice 54 is connected to one terminal of asource of alternating electrical energy 57 by a line 58 which passesthrough an aperture 59 provided in the tubular member 55. The otherterminal of the source of alternating electrical energy 57 is connectedto ground at 60. The accumulation of foreign particle in the innersurface 61 of the orifice 54 over a period of time would adverselyaffect the performance of the orifice. However, alternately placing apositive and negative charge on the orifice 54 will prevent such anaccumulation from forming. When the orifice 54 is charged positively,positively charged foreign particles present in the hydraulic fluid inthe vicinity of the orifice 54 will be repelled away from the innersurface 61 of the orifice toward the center of the fluid stream andcarried thereby away from this area. When the orifice 54 is chargednegatively, negatively charged foreign particles present in thehydraulic system in the vicinity of the orifice will be repelled awayfrom the inner surface 61 of the orifice toward the center of the fluidstream and carried thereby away from this area.

The sources of alternating electrical energy 18, 48, and 57 in FIGURESl, 2 and 3, respectively, should be of relatively low frequency. This isdesirable to permit the foreign particles which are repelled away fromthe surfaces of the critical parts of the system to be carried aconsiderable distance downstream by the hydraulic fluid before thepotential on the critical parts reverses and attracts such particles.For optimum results the frequency should be low enough to permit aparticular particle to flow completely through a critical part beforethe potential reverses. This frequency naturally will depend upon thevelocity imparted to the particle by the fluid stream and the length ofthe longest critical part of the system. It have determined thatexcellent results can be obtained in typical aircraft hydraulic systemsusing a source of alternating electrical potential having a frequency ofapproximately 2 cycles per second.

Although my invention basically consists of, and the attached drawingsand my description thereof to this point have been concerned with, aprocess and apparatus wherein an alternating electrical charge is placedon a critical part of a hydraulic system to alternately repel positivelyand negatively charged foreign particles in the hydraulic fluid, theremay be particular applications where it is desirable to subject thecritical part of the hydraulic system to a potential of constantpolarity. For instance if it should be determined that virtually all ofthe foreign particles in the hydraulic fluid are positively charged, thecritical part may be subjected to a positive electrical charge toprevent the accumulation of such particles. Similarly, if it isdetermined that a particular hydraulic fluid contains only negativelycharged foreign particles, the critical part may be subjected to anegative electrical charge to prevent the accumulation of suchparticles.

This invention may be performed and/or embodied in other ways withoutdeparting from the spirit or essential characteristics thereof. Theprocess and embodiments of my invention described herein are thereforeto be considered as in all respects illustrative and not restrictive,the scope of my invention being indicated by the appended claims, andall changes which come within the meaning and range of equivalency ofthe claims are intended to be embraced therein.

The invention claimed is:

1. In a hydraulic system utilizing a dielectric fluid, the improvementcomprising:

an electrically conductive valve body connected in said system;

means for electrically insulating said valve body from the otherelements of said system; and

means for impressing an electrical potential on said valve body wherebyany foreign particles in said fluid having an electrical charge of thesame polarity to that impressed on said valve body will be repelled awayfrom said valve body.

2. The apparatus of claim 1 wherein said means for impressing anelectrical potential on said valve body is adapted to impress analternating potential on said valve body.

3. The apparatus of claim 1 including additionally:

a tank connected into said hydraulic system; and

at least one electrode adapted to have a polarity opposite to that ofsaid valve body removably mounted in said tank and adapted to beimmersed in said fluid whereby said foreign particles will be collectedon said electrode.

4. In a hydraulic system utilizing a dielectric fluid, the

improvement comprising:

an electrically conductive valve body having a valve seat formedinternally thereof;

a valve member mounted internally of said valve body having a portionthereof configured to snuggly mate with said valve seat when in a firstposition and movable to a second position with said portion beingwithdrawn from contact with said valve seat;

means for electrically insulating said valve seat from a substantialportion of said valve body; and

means for impressing an electrical potential on said valve seat wherebyany foreign particle in said fluid having an electrical charge of thesame polarity to that impressed on said valve seat will be repelled awayfrom said valve seat.

5. The apparatus of claim 4 wherein said means for impressing anelectrical potential on said valve seat is adapted to impress analternating potential on said valve seat.

6. The apparatus of claim 4 including additionally:

a tank connected into said hydraulic system;

at least one electrode adapted to have a polarity opposite to that ofsaid valve seat removably mounted in said tank and adapted to beimmersed in said fluid whereby said foreign particles will be collectedon said electrode. 7. In a hydraulic system utilizing a dielectricfluid, the improvement comprising:

an electrically conductive fixed orifice;

means for electrically insulating said orificefrom the other elements ofsaid system; and

means for impressing an electrical potential on said orifice whereby anyforeign particles in said fluid having an electrical charge of the samepolarity to that impressed on said orifice will be repelled away fromsaid orifice.

8. The apparatus of claim 7 wherein said means for impressing anelectrical potential on said orifice is adapted to impress analternating potential on said orifice.

9. The apparatus of claim 7 including additionally:

a tank connected into said hydraulic system; and

at least one electrode adapted to have a polarity opposite to that ofsaid orifice removably mounted in said tank and adapted to be immersedin said fluid whereby said foreign particles will be collected on saidelectrode.

References Cited UNITED STATES PATENTS 2,116,509 5/1938 Cottrell 2043002,336,542. 12/1943 Hatfield 204-188 2,884,375 4/1959 Seelig 204l882,870,081 1/1959 Frey 204l84 1,825,477 9/1931 Riechart 204147 2,025,24312/1935 Jackson et al. 204147 2,077,505 4/1937 W0elflin 204l84 2,376,5355/1945 Fisher 2041 84 2,665,246 1/1954 Bates 204l84 HOWARD S. WILLIAMS,Primary Examiner.

JOSEPH REBOLD, JOHN R. SPECK, JOHN H. MACK,

Examiners.

E. ZAGARELLA, J. BATTIST, G. KAPLAN,

Assistant Examiners.

1. IN A HYDRAULIC SYSTEM UTILIZING A DIELECTRIC FLUID, THE IMPROVEMENTCOMPRISING: AN ELECTRICALLY CONDUCTIVE VALVE BODY CONNECTED IN SAIDSYSTEM; MEANS FOR ELECTRICALLY INSULATING SAID VALVE BODY FROM THE OTHERELEMENTS OF SAID SYSTEM; AND MEANS FOR IMPRESSING AN ELECTRICALPOTENTIAL ON SAID VALVE BODY WHEREBY ANY FOREIGN PARTICLES IN SAID FLUIDHAVING AN ELECTRICAL CHARGE OF THE SAME POLARITY TO THAT IMPRESSED ONSAID VALVE BODY WILL BE REPELLED AWAY FROM SAID VALVE BODY.